8 Old School Tips For Better Hand Filing

G’day Chris here, and welcome back to Clickspring. The hand file is about as old school as it
gets, so its a great first tool to kick off this
new series of engineering tips. And as much as I love working with the lathe
and mill, there are many occasions in the home shop
where hand fitting is the better way to go. So with that in mind, here’s 8 old school
tips, for better hand filing. First off, be sure to use only the best quality
files. Because the difference in durability and cut
quality when compared with the cheap imports is dramatic. You’ll see an immediate step change in the
quality of your work when using good files, and you’ll enjoy the process more because
they cut so well. I use Swiss made Grobet files for the vast
majority of my filing and I find them to be excellent. So If you’re looking to track some down, be sure to confirm that they are actually
made in Switzerland before you buy, and keep an eye out for the bunny on the tang. Number 2: Safe edges are enourmously useful
when precision filing. Although I have to admit, it goes against
every instinct to take an expensive new file and then deliberately blunt a cutting surface. But there really does need to be at least
some differential cutting ability within the file set. And virtually all of my files have at least
one safe edge ground onto them, if its not a natural feature of the file already. A safe edge like this effectively isolates
the cutting to a single surface, and it forms a key part of my filing technique. Because when I’m filing something that needs
to be precise, like for example a rectangle thats required
to be dead on center. I like to have the basic target profile formed, very early in the filing process, before I
use up too much of the available metal. This is a lot harder to achieve if the file
is cutting on 2 surfaces at once, so isolating the cutting to a single surface
at a time just makes it that much easier to control the outcome. Also, have a close look at the edges of the
files. Where the surfaces meet, there’s effectively
a bit of a radius to the cut. So the file can never give a corner that’s
any crisper than that. And often that’s just not good enough for
the final result. But with a safe edge ground onto one surface, at least two edges of the file become as crisp
as can be, and so can now deliver a sharp inside corner
on the workpiece. And while we’re on the subject of corners, they really are the key to the whole process. Because they essentially define the boundaries
of the surrounding surfaces. If a corner gets away from me, its pretty
much impossible to recover the work. So here’s the approach that I usually take
to make sure that doesn’t happen: First, when removing the waste stock I make
sure I leave some excess material over the object line, to give me something
work with . A millimeter or so usually works well, but
often I’ll leave a little more to play it safe. Next I identify the critical corners of the
workpiece. These are the locations that must be well
positioned for the part to be acceptable. And then I start the cut working directly
towards those corners, with the objective of establishing the overall
shape whilst using up as little of the metal margin
as possible. Ideally I’m aiming for a slightly under or
oversized version of the final profile just short of the line. As I get closer to the line, I shift to the
finer cut files, so that the rate of metal removal reduces,
and the surface finish starts to improve. Towards the very end, if its all going well,
then I can slowly work it the rest of the way. with light cuts, until I see the fit that
I want. And its not unusual for this last part of
the process to take up most of the time. Because there’s often only a handful of file
strokes between a tight and a perfect fit. The very last thing I want to do is take it
too far, and remove too much metal. Now this idea can be applied to just about
any profile, whether it be internal or external. But it is certainly more awkward to work on
an internal shape. And the fact that the initial opening is usually
a round hole, makes it easy to inadvertently tip the final
profile relative to the workpiece. But again its a clear focus on the corners
that keeps the whole thing on track. If I get the corners correctly established
early, then the orientation can be locked in. And the whole shape can be slowly worked toward
the final profile. Now of course that’s the ideal, but it rarely
goes according to the plan, which leads to tip Number 4. Once a surface starts to trend in the wrong
direction, it can very quickly get beyond a point that’s
recoverable. So I check the work often, making sure that
all is as it should be. And if I see a problem developing I’ll correct
that first. Now the earlier this happens the better. Its a lot more fun lightly coaxing a small
error back into shape, than it is to have to go deep into the margin
of metal to recover a well developed error, and so jeopardise the entire part. For something like this wheel a constant visual
check is enough to confirm that the apex of the cut is tracking
the marking out, and that the teeth aren’t being rolled to
one side or the other. But this cotter pin is a good example of where
both referencing the marking out and taking direct measurements is required. Much like I mentioned before, the aim is to
establish a slightly oversized profile, just outside the line. Again making sure that the key corners that
define the profile end up where they should be. But the shank on this part needs to have a
light taper to perform its locking role. So once the profile is close, direct measurement
becomes the better method to track whats happening for the final stage
of formation. Now there is an even more immediate technique
that can be used to pick up errors, as they occur. Just prior to each cut, a light cross grain
pattern can be made on the surface of the work, and then a light can be positioned to make
that pattern more visible. The first stroke on this pattern shows how
the file was oriented for the cut. And then with each subsequent stroke its very
easy to see exactly where the metal is being removed. I can immediately see if I’m rolling an edge,
and then adjust the cut on the fly to compensate. Its such a simple idea, and its incredibly
effective. Because it means that rather than reacting
after completing a surface, I can take a much more proactive approach
while the cut is in progress. And it makes creating a taper or dealing with
a localised error easier too. Just mark the region where more metal needs
to be removed, and then concentrate the work there. OK, so its clear that human factors play a
big role in the outcome when hand filing. There’s an unavoidable tendency for small
errors of movement, that needs to be somehow managed. And one thing I find useful for this are the
reference edges of whatever I’m using to hold the work. I watch those edges about as much as I watch
the file itself, because they quickly reveal any error in the
way I’m moving the file, and I can immediately correct what I’m doing. And although the effect is quite subtle, the
shop itself has a few reference edges too, that can also help the process. Aligning the work with the vise, and then
the vise with the bench means that all of these edges that are sitting
in my peripheral vision as I work, and can now also give me cues for better alignment
of the file. Now another way to manage the human errors
is to limit the entire movement to something that has less inclination to
drift. And a great example of this is draw filing. When holding the file for draw filing, the
file itself presents as a relatively long reference line, to visually confirm that the cut is being
performed square to the work. And the fact that its held with both hands means that there’s a good controlled grip
to keep it that way. So the technique is perfect for delivering
a very precise surface. Its also an excellent technique help generate
the same profile on 2 or more parts at the same time. And finally, just a quick word about filing
buttons and other filing guides. Its one thing to file a flat surface, but
something else entirely to freehand file circular shapes. So one way to make it a lot easier is to use
filing buttons. They don’t need to be anything fancy, generally just a simple shouldered bolt design
is all that’s required. Although there are two schools of thought
about what they should be made from. Some are strong advocates that they be made
of hardened steel, so that when reached the file can’t cut them. But of course that’s bad news for the files. So my personal choice is to turn them up on
the lathe from mild steel, and simply accept the possibility that they’ll
get slightly damaged over time. And the same idea can be expanded to generate
more complex shapes using guides, like for example the crossings on this wheel. The shape near the center of the wheel needs
to be exactly the same for each opening, and a filing guide makes this much easier
to achieve. OK, so that’s Old School Tips number one complete. And by no means is this meant to be a comprehensive
list, so be sure to add your own filing tips in
the comments below. Thanks for watching, I’ll see you later.


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